From among wireless transmission techniques, skills for increasing sector throughputs by using multiple antennas have been researched. The spatial division multiplexing (SDM) skill, a representative skill for increasing sector throughputs, acquires the multiplexing gain by transmitting different signals to a plurality of antennas. Also, the precoding SDM scheme for transmitting data streams by forming a plurality of beams having less interference between antennas by using multiple antennas increases the sector throughputs.
The scheme for a single base station to transmit singular or plural data streams to a plurality of terminals is called the spatial division multiple access (SDMA). It is applicable to the case of transmitting a signal in the downlink and the case of receiving a signal in the uplink.
In this instance, in order to acquire the effect of increasing the sector throughput by using the SDMA, it is required to concurrently transmit as large a plurality of data streams as possible, which is allowable only when the received signal to noise ratio (SNR) of a plurality of terminals undergoing multiple transmission is great. However, the spatial multiplexing is allowable only in an area that is near the base station having a great terminal SNR, and is difficult to be applied to a terminal that is distant from the base station. That is, the spatial multiplexing is only applicable to the partial region of a cell.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.